191 lines
4.9 KiB
Go
191 lines
4.9 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fuse
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import (
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"context"
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"fmt"
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"net"
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"os"
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"os/exec"
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"strings"
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"syscall"
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)
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// Server is an interface for any type that knows how to serve ops read from a
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// connection.
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type Server interface {
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// Read and serve ops from the supplied connection until EOF. Do not return
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// until all operations have been responded to. Must not be called more than
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// once.
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ServeOps(*Connection)
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}
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// Mount attempts to mount a file system on the given directory, using the
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// supplied Server to serve connection requests. It blocks until the file
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// system is successfully mounted.
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func Mount(
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dir string,
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server Server,
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config *MountConfig) (*MountedFileSystem, error) {
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// Sanity check: make sure the mount point exists and is a directory. This
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// saves us from some confusing errors later on OS X.
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if err := checkMountPoint(dir); err != nil {
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return nil, err
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}
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// Initialize the struct.
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mfs := &MountedFileSystem{
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dir: dir,
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joinStatusAvailable: make(chan struct{}),
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}
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// Begin the mounting process, which will continue in the background.
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ready := make(chan error, 1)
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dev, err := mount(dir, config, ready)
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if err != nil {
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return nil, fmt.Errorf("mount: %v", err)
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}
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// Choose a parent context for ops.
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cfgCopy := *config
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if cfgCopy.OpContext == nil {
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cfgCopy.OpContext = context.Background()
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}
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// Create a Connection object wrapping the device.
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connection, err := newConnection(
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cfgCopy,
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config.DebugLogger,
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config.ErrorLogger,
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dev)
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if err != nil {
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return nil, fmt.Errorf("newConnection: %v", err)
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}
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// Serve the connection in the background. When done, set the join status.
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go func() {
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server.ServeOps(connection)
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mfs.joinStatus = connection.close()
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close(mfs.joinStatusAvailable)
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}()
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// Wait for the mount process to complete.
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if err := <-ready; err != nil {
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return nil, fmt.Errorf("mount (background): %v", err)
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}
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return mfs, nil
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}
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func checkMountPoint(dir string) error {
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if strings.HasPrefix(dir, "/dev/fd") {
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return nil
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}
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fi, err := os.Stat(dir)
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switch {
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case os.IsNotExist(err):
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return err
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case err != nil:
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return fmt.Errorf("Statting mount point: %v", err)
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case !fi.IsDir():
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return fmt.Errorf("Mount point %s is not a directory", dir)
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}
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return nil
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}
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func fusermount(binary string, argv []string, additionalEnv []string, wait bool) (*os.File, error) {
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// Create a socket pair.
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fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
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if err != nil {
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return nil, fmt.Errorf("Socketpair: %v", err)
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}
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// Wrap the sockets into os.File objects that we will pass off to fusermount.
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writeFile := os.NewFile(uintptr(fds[0]), "fusermount-child-writes")
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defer writeFile.Close()
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readFile := os.NewFile(uintptr(fds[1]), "fusermount-parent-reads")
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defer readFile.Close()
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// Start fusermount/mount_macfuse/mount_osxfuse.
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cmd := exec.Command(binary, argv...)
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cmd.Env = append(os.Environ(), "_FUSE_COMMFD=3")
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cmd.Env = append(cmd.Env, additionalEnv...)
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cmd.ExtraFiles = []*os.File{writeFile}
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cmd.Stderr = os.Stderr
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// Run the command.
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if wait {
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err = cmd.Run()
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} else {
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err = cmd.Start()
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}
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if err != nil {
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return nil, fmt.Errorf("running %v: %v", binary, err)
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}
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// Wrap the socket file in a connection.
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c, err := net.FileConn(readFile)
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if err != nil {
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return nil, fmt.Errorf("FileConn: %v", err)
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}
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defer c.Close()
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// We expect to have a Unix domain socket.
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uc, ok := c.(*net.UnixConn)
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if !ok {
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return nil, fmt.Errorf("Expected UnixConn, got %T", c)
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}
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// Read a message.
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buf := make([]byte, 32) // expect 1 byte
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oob := make([]byte, 32) // expect 24 bytes
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_, oobn, _, _, err := uc.ReadMsgUnix(buf, oob)
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if err != nil {
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return nil, fmt.Errorf("ReadMsgUnix: %v", err)
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}
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// Parse the message.
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scms, err := syscall.ParseSocketControlMessage(oob[:oobn])
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if err != nil {
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return nil, fmt.Errorf("ParseSocketControlMessage: %v", err)
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}
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// We expect one message.
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if len(scms) != 1 {
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return nil, fmt.Errorf("expected 1 SocketControlMessage; got scms = %#v", scms)
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}
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scm := scms[0]
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// Pull out the FD returned by fusermount
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gotFds, err := syscall.ParseUnixRights(&scm)
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if err != nil {
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return nil, fmt.Errorf("syscall.ParseUnixRights: %v", err)
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}
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if len(gotFds) != 1 {
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return nil, fmt.Errorf("wanted 1 fd; got %#v", gotFds)
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}
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// Turn the FD into an os.File.
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return os.NewFile(uintptr(gotFds[0]), "/dev/fuse"), nil
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}
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